Reproduction of sound characteristics.



w. FULLER.

REPRODUCTION OF SOUND CHARACTERESHCS.

APPucATwN FILED SEPT-30, 1910. RENEWED JUNE 28. @922.

Invenfor Percy W. Fu'efer PERCY WHEATON FULLER, 0F BOSTON,MASSACHJJ'SETTS.

REPRODUCTION OF SOUND CHARACTERISTICS.

Specification of Letters Patent.

Patented Feb. 19, 19118.

Application filed September 30, 1910, Serial No. 584,731. Renewed June 28, 1917; Serial No. 117,595.

To all whom it may concern:

Be it known that I, 'PERCY WHEATON FULLER, a citizen of the United-States, residing at Boston, in the county of 'Sufiolfi and State ofMassachusetts, have invente certain new and useful Improvements Belatiue to Reproduction of Sound'Gharacteristics, of which the followingdescription, in

.on each other and then connecting the sheets in a manner here nafterspecified with a circuit arranged to ave an undulating current therein,the undulations of Which vary according to the sound-characteristics tobe reproduced.

In order to give a complete understanding of the invention, I will-firstdescribe a selected embodiment thereof and then point out the novelfeatures in the appended claim. The drawings show diametrically a deviceembodying my invention. The reproducer is in the form of condenser madeby superposing sheets of very thin pure tin fo l and sheets of asuitable dielectric material, such as oiled silk or relativelypuncture-proof paper or itsequivalent, said sheetsbeing arrangedalternately and laid-loosely on each other. The alternate sheets of tinfoil are electrically connected together and connected to one side ,of acircuit and the other sheets of tin foil are electrically connectedtogether and connected to the other side of 4 the. circuit, said sheetsall lying loosely one,

on the other and without mechanical pressure. Means are providedtoproduce an-undulating current in the circuitcon'nected to thereproducer, which undulating current has variations correspondingtol thesound characteristics to be reproduced. The condenser or reproducer'thus constructed 1s shown generally at 8, wherein it is indicated moreor less diagrammatically. In pract1ce I propose to use aboutone hundredsheets or very thin pure tin foil which are smooth and fiat and aboutone hundred sheetsofthln smooth puncture-proof paper. Th1s paper may beprepared by immersing each sheet-- in and evenly impregnating it withpure melted paraflin wax, wax be ng preferably selected for this purposeWhIGh. has a high melting point. The Wax-coated sheets constituteflexible dielectric leaves. While these sheets may have any suitablesize, I prefer to haveeach sheet approximately five and a half'by-eightand aquarter inches. The sheets are superposed one on another andarranged so that the sheets" of tin foil anddielectric materialalternate with each other. Said sheets are loosely placed on each other,andare, therefore, free to vibrate and for the purpose of my inventionit is of importance that. theqt alities of light weight and flexibilitybe'com ined in the'highest attain- 'able degree and also'that the sheetsshould all he as smoothly together as possiblewithout mechanicalpressure. The alternate tin foilsheets are electrically connectedtogether and are connected to one side of a circuit including a suitablesource '0 of constant electr'or motive force of about two hundred andfifty to three hundred voltsl Theremaining'tin foil sheets'are alsoelectrically connected together and connected to the other side'of'saidcircuiti This circuit connects at u" with the terminals of thesecondary-winding of an induction coil u. l The primary winding u v ofthis induction coil is connected to an apparatus designed to produce avariable current in'said circuit, which current varies in accordance'with the varia tions of the sound characteristics desired to bereproduced. The varyingcurrent in the primary of the induction coilproduces inductively a correspondingly variable current in thesecondary. of said coiland this produces corresponding variations in thecharge of the condenser s. The'source of electromotive force 22 impartsto the condenser an initial charge which places'it under initial stress.The v.efiect of the variable currentproduced in, the cicuit connectingwith the condenser isvto throw the flexible dielectric leaves ofsaidcondenser or reproducer into vibration, and such vibration will cause arecord-bearing ribbon d havin thereon a deposit of magnetically:permeabe metal which varies at difi'erent polnts along the ribbon in accordancewith the variations in the quality, pitch and voluine of the soundsrecorded. This ribbon is shown as extending through an aperture in" twopole pieces h, h

of a magnet yoke g, said ribbon passing over dire'ction pulleys w, andthe ends thereof being wound on the two spools e. w indicates a coil ofconducting wire which is mounted on-the pole pieces h,-h in such amanneras to inclose the gap between the pole pieces The terminals of the coilto are connected to the .primaryu. of the induction coil u. As therecord ribbon at is wound from one spool 0" onto the other spool andpasses'throughthe coil 10, a variable currentis induced in saidcoil, thevariations of which correspond to the variations in the deposit of themagnetically-permeable metal on the ribbon d by reason of the fact thatthe varying amounts of, the deposit at different points cause avariation in the amount of reluctance to the on theribbon cl, and'suchvarying current causes vibrations which reproduce the sound,

as above described. I wish to state, however, that this particular Wayof producing the ters Patent is desired variations in the primarywinding of the induction coil u isnot essential to the invention.

While I have herein described one'embodimentof my invention, 1 do notwish to belimited to the constructional details 'sliownl.

Having fully described my inventiomwv-hat I claim as new and desire Inadevice of the blnation with a reproducer comprising a phi-'- rality'ofsheets of tinfoil-and flexible dielectric material arranged alternatelyand sir-- perposed one on thefother' loosely in a horizontal positionand without mechanical pressure, of a direct current circuit of twohunedreclandfifty to three hundred'volts, one

side of which is connected to thealternate sheets ofjtin foil and theothersi de of which is connected-to the other sheets of tinfoil,

sound characteristics to jbe reproducech PERCY WHEATON FULLER-Witnesses: I

ALEXANDER O. MACKAY, JoHN C SHnRMaN. v

class described, the. cointo secure bykLetT 4 i v and means to impresson the direct current clrcult an undulating currenthavnig varia-' tionscorrespond ng to the 'XillfliltlOIlS of

